Standard Member

Just been wondering why a grey screen is recommended for lower contrast LCD projectors? Any change to the surface of the screen will affect all light reflected (i.e. blacks and whites), so it cannot enhance the contrast in any way. Is it simply that a darker picture with blacker blacks looks better than a brighter picture with less black blacks even though the contrast ratio will be the same?

Well-known Member

If you projected onto a white and grey screen in outer space then your observation would be true however, light does bounce off the screen and hit its surroundings (walls/ceiling etc...) and then gets bounced back to the screen which causes a loss of contrast ratio.

Active Member

Since contrast ratio is more of an issue in most cases than light output of the projector, a grey screen is often used to compensate for the lack in performance in terms of black vs white (contrast).

So, a grey screen changes your perception of contrast, but not the contrast of the projected image, which is determined by the active component in this equation: the projector.

The function of the screen is to reflect the image projected in the best way possible. The screen is not a device which can change the projected image.
It can only change the way in which the light bounces back from the screen. The more the angle in which it is reflected, is reduced, the more the light is focused/concentrated. The amount to which this is done, is expressed in the term "Gain". More Gain does not mean more light coming back, it just means the light is more focused, when it bounces back from the screen. A higher Gain thus also reduces the viewing angle.